Deff. a 454, it appears to be factory but I would want to make sure of that, hard telling what people have done, if they did take the time to swap it hopefully they used the right mounts and got the alignment right, 738hrs is nothing as long as the engine has been maintained which the rest of the boat indicates that it has been very well.
As an owner of a 92' composite boat I would jump all over that boat in that condition & with those hours, of course I would try to get it for 10g but would not pass it up at 12g either. You are not going to get into a comparable I/O (junk) for less than 15g.
A test drive is your best bet!!
Good luck, hope it all works out for you